A photopolymerizable composition is used for the fabrication of printed circuit boards. Namely, a printed circuit board is fabricated in the following manner. For example, the copper surface of a copper-coated substrate is first of all coated with a composition which is a solution of a photopolymerizable resin or a photopolymerizable film formed beforehand into the shape of a film is laminated on the copper surface of the copper-coated substrate, whereby a resist film is formed. The resist film is next exposed imagewise to radiation and thereafter developed with a solvent or an aqueous alkaline solution to form a resist pattern on the copper-coated substrate. Copper surface areas not protected by the resist pattern are subjected to selective etching, metal plating or the like to fabricate a printed circuit board.
To improve the working efficiency, air pollution problem and yield, dry film resists are used in recent years. These dry film resists can be developed with an aqueous alkaline solution. They are three-layered laminates having flexibility, namely, are formed of a base film layer, a photopolymerizable resin layer and a protective film.
As photopolymerizable compositions which can be developed with an aqueous alkaline solution, are generally used those composed of an acrylic copolymer containing carboxyl, amino or hydroxyl groups, a photopolymerizable monomer and a photoinitiator.
Such photopolymerizable compositions are etched and removed with an aqueous strong alkaline solution. However, their etching are very time-consuming. As a consequence, a copper wiring or a solder plating layer provided over the copper wiring is corroded with the strongly alkaline etchant so that the wiring patter may be partly lost or cut off. If the solder plating employed as an etching mask upon etching the copper surface area is corroded with an etchant, the solder plating would no longer be used as an etching mask.